var q1 = from orderitem in q2

                     join pd in _iProductDetailContract.Entities on orderitem.ProductDetailId equals pd.Id

                     join pm in ProductMainContract.Entities on pd.ProductMainId equals pm.Id

                     join user in UserContract.Entities on pm.BuyerId equals user.Id

                     into orderItemBuyer

                     from user in orderItemBuyer.DefaultIfEmpty()

                     group new { orderitem.Price, orderitem.Num }

                     by new { orderitem.ProductDetailId, orderitem.Name, orderitem.Size, orderitem.Price, pm.AliasName, BuyerName = user.Name }

                     into g

                     orderby g.Sum(p => p.Num) descending

                     select new

                     {

                         ProductDetailId = g.Key.ProductDetailId,

                         Name = g.Key.Name,

                         Size = g.Key.Size,

                         AliasName = g.Key.AliasName,

                         BuyerName = g.Key.BuyerName,

                         Num = g.Sum(p => p.Num),

                         Price = g.Key.Price,

                         TotlePrice = g.Sum(p => p.Num * p.Price)

                     }

                     ;